Method and apparatus for burning fuel



July 10, 1951 w. J. BLOOMER 2,560,076

METHOD AND APPARATUS FOR BURNING FUEL 2 Sheets-Sheet 1 Filed June 14, 1949 7, Alyz INVENTOR.

Wardjfijhamr lm Y July 10, 1951 w. J. BLOOMER I 2,560,076,

' METHOD AND APPARATUS FOR BURNING FUEL Filed June 14, 1949 2 Sheets-Sheet 2 IN VEN TOR.

Patented July 10, 1951 UNITED STATES PATENT GFFICE METHOD AND APPIURIIQI'fUS FOR BURNING Ward J. Bloomer, Westfield, N. 3., assignor to The Lummus Company, New York, N. Y., a corporation of Delaware Application June 14, 1949, Serial No. 98,976

. tion, now abandoned.

It is an object of this invention to provide such a burner and such a method, wherein a high efiiciency and completeness of combustion is achieved through entrainment or injection of the fuel into a swirling annular layer or hollow column of combustion air in which thefuel is mixed vide such a burner and such a method, wherein all of the air utilized to entrain liquid fuel and break, separate or atomize it into a mixture or suspension comprising small air-borne fuel particles is utilized also as combustion air, i. e., wherein a column of low-pressure air is made to perform the multiple functions of breaking the fuel into discrete particles of such size as are readily combustible, of entraining the aforesaid particles and suspending them uniformly therein, and conveying the aforesaid particles in uniform suspension to a burning zone, separated or spaced from the zone or zones wherein they are entrained and mixed while also supplying the greater portion, at least, of the air necessary for combustion.

It is a further object of this invention to provide a burner particularly adapted to the method of this invention and possessed of features whereby it may be adjusted. to accommodate varying types and grades of fuel and varying air pressures and whereby the burner may be cleared of slugs" or obstructions impairing the efficiency thereof during its operation.

This application is also a continuation-in-part of my copending application Serial No. 66,445, filed December 21, 1948, for improvements in Method and Apparatus for Burning Fuel. In that application the mixing zone inside the bladed tuyere was surrounded by the entrainment zone which was disposed outside the tuyere, fuel being entrained in air by its passage through the blades or vanes of the tuyere into the mixing zone within the tuyre. According to this invention the entrainment zone is disposed at or in the lower end of the mixing zone formed by the hollow, swirling outwardly moving fuel-air column. In other words, the entrainment zone is within the tuyre, and the fuel is introduced or injected directly into the inner end or lower end portion of the swirling air column, without passage through the blades or vanes whence it passes outwardly through the Y mixing zone formed by the swirling fuel-air mixture representing, so to speak, the main wall portion of the hollow column within the tuyre, passing thence to the combustion zone which is spaced outwardly from the tuyre.

It is a further object of this invention to provide such a burner and such a method which in addition to being adapted to gaseous and finely divided or comminuted solid fuels or combinations thereof is particularly adapted to liquid fuels wherein the aforesaid breaking of liquid fuel into the small readily combustible particles is followed by a shearing action on the particles whereby a high combustion rate is accomplished in a small volumetric space.

'A further object of the invention is to provide a commercial burner assembly including associated wind box, primary air controls, fixed cylindrical tuyere and mounting plate whereby the entire assembly can be readily attached to and/or detached from a furnace.

These and other objects and advantages of the invention will clearly appear from the following description thereof taken in conjunction with the drawings in which:

Fig. 1 is a diagrammatic view in elevation, with parts in section, of apparatus adapted to burn liquid fuel;

Fig. 2 is a horizontal section taken substantially on the plane indicated by the line 2-2 in Fig. 1;

Fig. 3 is a fragmentary section taken substan-'- tially on the plane indicated by the line 3-3 in Fig. 1;

Fig. 4 is a substantially central vertical section through a part of a furnace setting showing a horizontally mounted burner;

Fig. 5 is a vertical section on the line 5-5 of Fig. 4 of the modified form of tuyere having a supplementary air feed and shield.

Referring to the drawing in detail, and as shown particularly in Figs. 1 to. 3, the burner. comprises a tuyere generally designated Ill, surrounded by a shell or casing generally designated II, the space between the shell and tuyere being closed at its outer end by an annular, substantially frusto-conical end plate 12 provided with an orifice closely fitting the tuyere ID. The end plate I2 is fixed, in a suitable manner, both to the upper or outer ends of the blades of the tuyere I0, and to'the outer end of the shell or casing ll.

At its lower end, the shell or casing H is provided with a flange I4 which is bolted or otherwise secured at If; to a flange H in which the delivery duct I9 of the blower 20 terminates. The blower 20 is provided with an inlet duct 2| through which air is drawn and forced through the blower 20 upwardly through the delivery or outlet duct l9 and axially into the shell or casing H, whence it passes inwardly through the blades or vanes of the tuyere ID to form a swirling, hollow column of air for a purpose hereinafter described in detail.

The tuyere I comprises a plurality of spaced substantially tangential blades or vanes 22, having their upper or outer ends fixed to the above described end plate l2, and their lower or inner ends fixed to a seat 23 provided on the tuyere base plate 25. The series of tangential blades form the sidewall of the tuyre II), the slots or spaces therebetween, which are designated 24, providing a plurality of elongated substantially rectangular air inlets, spaces or air paths, through which the low-pressure air from the interior of the casing I I passes into the interior of the tuyere ID to form the above described swirling, outwardly moving hollow column of air.

The base plate 25 is provided internally with a fuel chamber 26 disposed substantially coaxially with respect to the tuyere I0 and communicating with a frusto-conical seat 2'! leading thereto. The base plate 25 is also provided with a centrally arranged packing gland generally designated 28, through which extends the threaded stem 29 of a mushroom-type valve member 30 having the periphery of the head portion thereof substantially complementary with the above described frusto-com'cal seat 21. This valve member 30 may be moved rotatably and/or axially with respect to the gland 28 by means, and for a purpose, hereinafter fully explained.

The space between the periphery of the valve 30 and the seat 21 forms an annular inlet or injection orifice 2611 through which fuel from the fuel chamber 25 may pass upwardly and outwardly directly into the swirling, hollow column of air formed by passage of the low-pressure air from the interior of the casing ll through the air inlets, spaces or air paths 24 into the interior of the tuyre l0. By axial adjustment of the valve 30. with respect to the seat 21, as hereinafter described, the area or size of the injection orifice 25a may be varied to accommodate fuels of various grades or types.

Fuel is supplied to the fuel chamber 25 by means of the pipe-like inlet 32 extending radially from the base plate 25 and preferably formed integrally therewith, as shown, through the wall of the shell or casing II to which it is secured in fluid tight manner, as by means of welding 33, as shown. The outer end of this inlet 32 is preferably secured in suitable manner as by a union 34 with the delivery 35 of fluid supply means under suitable pressure. Thus, fuel from the delivery pipe 35 passes into the fuel chamber 25 and is then supplied or injected upwardly and outwardly through the orifice 25a defined by the seat 21 and the periphery of valve 30 directly into the lower end portion of the swirling outwardly moving hollow column of air, as

4 shown in Fig. 1, being broken up into fine particles and thoroughly mixed with the air to form a uniform fuel-air mixture or suspension, which is readily combustible.

As will be readily understood, by varying the size of the orifice, by adjusting the valve 30, the rate of feed of a given fuel may be varied according to the pressure of air in the shell or casing l l, and the variation thereof likewise permits of the use of liquid fuels of widely varying properties in the burner system.

The means for accomplishing the above described rotary and/or axial adjustment of the valve 30, with respect to the base plate 25 and the seat 21, comprises the worm wheel 39 screw threadedly attached to the threaded stem 29 of the valve 30 and a cooperating worm 40. The worm wheel 39 is supported at its upper end by a suitable hearing or seat provided for that purpose in the base plate 25 and at its lower end by a seator bearing surface provided in the supporting bracket 4| which has the legs thereof fixedly secured, as by means of bolts 42, to the inner side of the base plate 25 in such manner that it is rigidly secured thereto. A pair of aligned similar supporting brackets 43 spaced axially with respect to the worm 40 support the worm for rotation without axial movement, and the shaft 44 extending from one end of the worm 40 is supported by a fluid tight bearing 45 supported in the wall of the shell or casing ll through which the shaft 44 extends, the shaft 44 being provided at its outer end with suitable manually operable means such as the crank 46.

The pitch of the screw threads in the worm Wheel 39 and the valve stem 29 is sufliciently steep to prevent relative rotation therebetween when the worm wheel 39is revolved through the crank 45. The valve member 30, however, is provided with means such as the sockets 3| which may be engaged by a suitable tool such as a spanner to hold the valve 30 stationary when the worm 40 is revolved whereby rotary movement of the worm wheel 39 is transmitted into axial movement of the valve 30 to increase or decrease the size of the feed or injection aperture. Likewise, the spanner or other tool may be revolved, without actuation of the crank 45 to cause relative rotary movement with respect to the worm wheel 39 and the valve 30 which is, of course, converted into axial movement of the valve 30 for the same purpose. The nature of the worm and wheel is such that the worm thus acts as a locking member, preventing such rotation of the valve 30 from revolving the worm wheel 39.

If the orifice between the valve 30 and the seat 21 becomes plugged up, or if the fuel causes the deposition of gum or other solid matter therein, revolution of the valve member 30 through the crank 46 may be accomplished to free the orifice of the obstruction without shutting down the burner, and without changing the adjustment of the valve 30.

While the above description relates to liquid fuel, and while the source of liquid fuel is shown in Fig. 1, it is, of course, to be understood that the above structure may be readily modified for use with gaseous or fluidized powdered or comminuted solid fuel by connecting the inlet 32 or 52 to such a source, in a manner which will be readily understood by those skilled in the art.

Operation An important feature of this invention is the production of a fuel-air suspension in the form of an open, swirling vortical fuel-aircolumn desi nated 50 in Fig. 1. As a result of the high velocity of air passing through the blades, this column 60 is unclosed, or open, throughout, its length and has a reduced pressure center. The setting up of forces acting in opposition to the vertical or outward linear velocity component of the fuel particles is obviated so that the fuel particles traveL freely and generally spirally out.- wardly through the tuyere. They are thus thoroughly mixed with or suspended in air from the entrainment zone adjacent the junction of the injection orifice with the interior of the tuyere I0, through the adjacent mixing zone 62 extending substantially throughout the length of the tuyere, to the burning zone 63. This latter zone is so spaced from the casing or shell H, and other parts of the burner, as to relieve these parts of the necessity for withstanding combustion 'temperature.

While this column 60 is herein described as "generally cylindrical, as hollow and open throughout its length, which is necessary in such a fuel-air column to achieve the objects and advantages of this invention, it might, perhaps, more accurately or mathematically be described as parabolic or truncated parabolic the inner surface being defined by a parabola of revolulion with its theoretical vertex lying below or outside the end wall of the tuyre III, which is formed by the valve 30 described above.

Because of the spacing of the burning zone or a surface generated by rotation of a parabola about an axis perpendicular to the base so that the increase in cross sectional area is comparatively slow as compared with the outward movement of the column of the fuel-air mixture to the flame of combustion. In such a construction unusually good combustion results.

The refractory curb or combustion chamber permits a stable sustained combustion in part also apparently because of the re-radiation of the 1 heat back from the curb to the burning fuel partoward the upper end of the casing ll, thence through the air inlets 24, between the blades 22 of the tuyere, into the tuyere l0, and thence outwardly as a vortex or helical path from the open end of the tuyere 10. The fuel pump, or other fuelsupply means, as the case may be, is then combustion zone from the mixing zone and entrainment zone, the separate particles of fuel pass, generally speaking, in spiral or helical aths in fully dispersed air borne condition, whereby substantially complete combustion thereof is achieved in the burning zone.

If forces in opposition to the outward or linear velocity of the fuel column (which are herein obviated) did exist, there would be a tendency for these separate fuel particles to fallout of suspension, which would materially impair the efliciency of the combustion, since the uniformity of the fuel-air suspension supplied to the burning zone 63 would be impaired or destroyed, resulting in periodic fluctuations which would produce, intermittently or periodically, incomplete combustion.

Closing of the column 60 at the bottom of the tuyre l0, would result in the production of such deleterious forces in opposition to the aforesaid outward or linear velocity of the component of the swirling fuel-air column, and consequent impairment of the uniformity of the suspension and the uniformity of the outward component of this velocity which are the factors upon which uniformity of combustion is dependent.

I find that it is not only necessary to provide the previously described column of helical moving air-fuel mixture, but that great care must be used to prevent a premature discharge of the fuel from the mixture which may occur from a sudden change of velocity as the mixture moves out of the restricted tuyere area. As one effective manner of accomplishing this, I provide a curb or refractory chamber 65 adjacent the end of the tuyere such-chamber being adapted to embrace and be mounted upon the top plate I 2 of the tuyere.

' In small furnaces with relatively low heat input, and with air pressures and velocities near the minimum that will successfully operate with this type of burner, I consider it-especially desirable to form the inner wall 66 of the curb as bustion occurs.

started, and fuel is supplied at a suitable rate to the fuel chamber 26 whence it passes upwardly and outwardly through the frusto-conical orifice provided by the seat 21 and the valve 30 into the tuyre and thus into the air vortex by which it is entrained, and thence through the mixing zone 62, through which it travels in a substantially helical path, bein thoroughly broken up and mixedor suspended in the current of air in the column 60, passing thence outwardly within this column to the burning zone 63 where com- Such combustion may be initiated by a torch or flame.

The vortical movement of the fuel and air within the mixer also causes a low pressure central region in the central region of the combustion zone in which the pressure is so low as to induce into the central path a body which is held over the center of the tuyre. This vortical movement tends to induce some of the hot gases from the combustion chamber as well as a portion of the flame itself into the tuyre so that the heat from the combustion chamber thus heats the fuel and air within the burner for some preheating. This results in highly eflicient combustion.

From the above description, it will clearlyappear that I have provided a new and improvedfuel burner adapted to burn fuel of widely varyin properties and characteristics, which burner is extremely self-contained and compact, and which contains no moving parts except, of course, the valve adjustment means of Figs. 1, 2 and3.

It will further appear that I have provideda new and improved method of burning fuel wherein fuel, either in gaseous, liquid or finely comminuted solid form, is entrained in a vortical' may be adjusted by damper Ila and .of the initlal velocity of the air column impressed upon the burner. It is also dependent upon the ratio of the diameter of the tuyere III to the length of the blades or vanes 22. For example, doubling the tuyere diameter, and halving the blade length, while providing the same blade area, pressure drop and air capacity in the burner provides four times the cross-sectional area in the orifice defined by the outer end of the tuyere III. For this reason, the net axial discharge velocity would be reduced and the pattern of the combustion zone would thus be varied accordingly by variation of the diameter-height ratio.

The term air as used herein is to be broadly construed, i. e., it is used broadly, to designate combustion supporting media including gases other than air and mixtures of such gases with air.

The angle of the blades and their relative length and the eifective openin will vary for different results, but in general I find it desirable to keep the blades about 0.39 inch in width, with an opening of Generally a. blade angularity of about 13 55' on a 7" diameter tuyere is appropriate. The essential element, however, is the relatively high velocity of air required to pick up the fuel. While I have operated at as low as 30 feet per second, usually I find a minimum of 50 feet per second to be necessary for uniform operation and the top range may be 100 feet per second or more. Higher ranges of 150 feet per second have been used but the pressure drop is excessive and if such a large capacity is required, then a larger tuyre should be used. For practical purposes the range of my burner is about 70% of design capacity to 140% of design capacity. The pressure drop in such case will'vary from about 3 of water to about 12" of water. With one pound per sq. in. gauge which is equal to 27.7" of water, I obtained 216% of designed working range.

The following table gives the approximate size of burners heretofore constructed and tested:

l NorE.-MM equals 1 million B. t. u./hr. of heat release.

The following table gives the details of a particular burner:

Length of tuyere3 /4 Diameter of tuyre-B Number of blades-48 Width of blades-0.525 inch Area of inlets, total-4.08 sq. in. or 0.0284 sq. ft.

Gross sectional area of tuyre7.06 sq. in. or

0.049 sq. ft.

Ratio inlet area to cross sectional area-0.58

Diameter of easing l l-6 inches Diameter of fuel pan--4 inches Air pressure in casing ll0.58 lb. per sq. in.

Air feed rate200 cu. ft. per min.

Fuel gas heating value-550 B. t. u./cu. ft.

Fuel rate-44.5 cu. ft./min.

Combined feed-244 cu. ft./ min.

Volumetric ratio of air to gas-4.5 to 1 Combined feed velocity8640 ft. per min.

Combined vertical feed velocity-5000 ft. per min.

Pressure drop through tuyeres16 inches of water 'Minimum pressure drop for satisfactory operation3 inches of water Heat release-1,468,000 B. t. u. per hour In the above case, the ratioof inlet area to cross sectional area of 58% will result in a low forward component of the fuel-air vortex. My experience has been that with ratios of from tag a much greater forward velocity could be obtained which in certain cases, provides a better flame pattern.

The same burner, under the same conditions using 41.3 A. P. I. kerosene weighing 6.818 lbs. per gal. and having a heat value of 19,810 B. t. u. per lb. burned 8.8 gal. per hour equal to a heat release of 1,128,600 B; t. u. per hour.

The same burner, when charged with powdered coal of 12,000 B. t. u. per 1b., supplied at the rate of 64.5 lbs. per hour, the other conditions being the same, gave a heat release of 769,000 B. t. u. per hour.

A further example of capacity is illustrated by a somewhatlarger tuyre. In this case a tuyre of 5% inches in height and 5 inches in diameter mounted in an 8 inch casing was supplied with a gas of 550 B. t. u. per cu. ft. heat value of the rate of 181.7 cu. ft. per min to release 6,000,000 B. t. u. per hour.

While, as above described, the low pressure air which entrains the fuel becomes combustion air, i. e., all of it takes part in fuel combustion, other, secondary air may be added to this low pressure air where the combustion air requirements are greater than this low pressure air.

The application of the foregoing general principles may also be applied to a horizontal type of burner. While it could be expected that a fluid fuel would normally tend to drain away from the high point of the tuyere, with a nonuniform flame, this was not a fact if the feed head closely fit the end of the tuyere. In such a case the feed of fuel is suitably accomplished at only sufficient head to maintain the feed pan full and by starting the air first, the flame is uniform.

The advantage of this discovery is of major importance for many furnace installations require a wall burner, not only for accessibility but also for uniformity of heating. A commercial burner mounting of this type which is adaptable to a furnace side wall is shown in Fig. 4.. The burner mounting 10 in this case includes the tuyere 12, its feed pan 13, the primary air duct 14, the wind box 15 and the controls all in an integral unit. Fuel is fed from pan 13 into the tuyre 12 through a substantially annular slot 13a. In this manner, the entire burner mounting 10 may be bolted to the furnace plate 11 as by bolts 18 and the entire unit is in place.

It is only necessary to connect the fuel line at 19 and the air intake at 80 and the unit can be placed in operation at once. A fixed position of the burner from the combustion chamber 82 is assured and operating variables are reduced to a minimum.

It will also be noted that the forward end of the primary air casing H in which the tuyre 12 is mounted, extends to the outer edge of the combustion chamber 82 formed in the furnace wall 84 by'the lining 85. The diameter of the combustion chamber 82 is preferably from one and a half to three times the diameter of the tuyere opening and it should be about as long in front of the tuyre as it is in diameter. The tuyereflz itself is thus actually outside of the furnace and in a zone of relatively low temperature. It is generally surrounded wtih refractory at 86 which may have a plurality of rows of secondary air ports 86:: and 86b connecting the wind box 15 with the combustion chamber.

The secondary air may be brought into the windbox through port 88 and I prefer to use a louvred member 90 with a movable louvred valve plate 9| to vary the air. This plate 9| may have a handle 92 to permit adjustment during operation, if necessary, bringing more or less of the fixed louvre openings into coincidence with the movable openings.

The tuyere 12 may have two sets of blades 12a and 12b and be provided with a generally cylindrical skirt 94 which closely embraces the blades near their center line and is secured in position by suitable means. The skirt has an effective diameter such that approximately equal amounts of air passing through the main air duct 14 go through the respective blade banks. In large type units, operating under high air velocity, there might otherwise be a tendency to channel the air which may easily be corrected by this device.

Although this very intimate mix carries the fuel particles in a number of turns in a helical path through the tuyre, the path itself is substantially smooth and uniform with a minimum of pressure drop. The air undoubtedly moves faster than the fuel particles however, causing a shearing of the fuel pa irjgy les so that there is a complete dispersion of the fuel particles in a highly atomized or mixed form. After the desired amount of mixing, the air-fuel mix is thrown out into the combustion chamber 82 in which combustion is completed within a very short distance.

As in the prior case the blades may be struck out of a suitable metal which need not be completely heat resistant itself. I find that although temperatures of several thousand degrees. Fahrenheit are generated in front of the burner, the rapid passage of air tends to keep the blades relatively cool. Long life of blades has been attained by using the various alloy steels such as 18% nickel, 8% chrome, and others. Preferably the blades are straight throughout their length to simplify their fabrication.

When preheated air is used to aid in reducing the viscosity of the fuel, as for example use of 450 F. preheated air on asphalt or 250 F. air on Bunker C, to establish a fuel viscosity having from 20 to 30 centipoises and thus exceptionally high heat release, the tuyere face 120 unless covered by refractory as in Fig. 2 becomes excessively hot. This is of course due to the radiation from the furnace and as the blades of the tuyere extend from the face plate to the fuel feed pan 13, some premature coking may take place.

As shown in Fig. 5, I have found that the mounting of a face plate shield Ma extending from the casing 14 to be especially effective. This shield which may be of a suitable heat resisting alloy such as 25% chrome and 12% nickel extends substantially parallel to the face plate 129 and to a position not beyond the plane of the end of the tuyere so that it does not interfere with the discharge of the fuel-air column. It may be provided also with two rows of apertures or air ports 12d.

The air which passes through ports 12d under the shield tends to cool not only the shield but also tends to cool and insulate the face plate 120. In operation, I have found that the temperature 10 at the end of the tuyere 12 may be reduced from approximately 1500 F. to approximately 450 F. and thus avoid any coking.

The principal advantage of the internal or inside fuel feed is that the pressure drop of the blades is materially reduced so that either more fuel is delivered or less pressure drop is taken for the same size of tuyere. In addition, the presence of the fuel within the tuyere tends to reduce wetting of the blades and reduces any tendency of the fuel to coke. With solid comminuted fuels, there is no attrition on the blades which might otherwise be objectionable. In each case of inside feed the fuel is distributed to a zone between the inside and outside walls of the air column whereby entrainment is readily accomplished. If the fuel is introduced to the center of the tuyere, it is resisted by the high speed rotation and centripetal resistance of the internal wall of the air column. With an increased velocity of the inlet air, the column 60 tends to become more nearly cylindrical and the fuel should be introduced closer to the tuyere wall to avoid a central unburned jet which otherwise results.

It is, of course, to be understood that the above description is merely illustrative and in nowise limiting, and that I desire to comprehend within my invention such modifications as are included in the scope of the following claims.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A method of burning fluid fuel utilizing a cylindrical mixing chamber open at its outer end and closed at its inner end, and having an annular side wall formed with a plurality of circumferentially spaced tangential air inlet slots extending to the closed inner end, and a casing surrounding the mixing chamber and closed at the outer end, said method comprising feeding air axially of said casing and over the length of the slotted side wall of the mixing chamber to direct the air through the slots and tangentially into the mixing chamber, said air being fed at such rate and angular relation to the axis of the mixing chamber that there is formed an outwardly moving rotating column of air with a partial vacuum in the center thereof, supplying fuel annularly to the inside of the mixing chamber adjacent the side wall at the closed inner end thereof and entraining said fuel by contact with the portion of air entering the inner end parts of the slots with said fuel being intimately mixed into and moved outwardly with the rotating column of air as an annulus along'the wall of the tuyere, discharging the fuel-air mixture as a vortical column into a combustion zone of elongated restricted circular cross section spaced outwardly from said mixing chamber, constraining the fuel-air mixture discharged into said combustion zone to a rotating outwardly moving hollow. column and burning said fuel-air mixture in said combustion zone as a continued rotating annulus.

2. ma fluid fuel burner, a tuyere having its side wall formed by a plurality of fixed generally tangentially disposed blades extending substantially throughout the length of the tuyere and forming inwardly directed air inlets therebetween, said tuyre being open at one end and having fuel feeding means within the interior thereof adjacent its opposite end, said fuel feeding means forming an airtight end for the tuyere, means for supplying fuel through said fuel feeding means axially into said last named end of said tuyre adjacent the inner edges of at least some of said air inlets, means for supplying air through said air inlets between said blades for forming a hollow swirling outwardly'moving column adjacent the inner wall of said tuyre and an inwardly moving central core, said column comprising a combustible fuel-air mixture, means at the inner end of the last-mentioned means and directed axially of the tuyre for supplying air under pressure, and an elongated combustion chamber registering with the outlet of said tuyere, said chamber having a refractory wall larger than the 'tuyere outlet but small enough to restrict the lateral component of the fuel-air mixture as it discharges from the tuyre, said combustion chamber having a diameter of from 1 to 3 times the diameter of the tuyere opening.

3. In a fluid fuel burner, a tuyere for mixing air and fuel and for discharging the combustible fuel-air mixture into an adjacent combustion chamber said tuyre having its side wall formed by a plurality of fixed, annularly-spaced blades projecting from the wall throughout substantially the entire length of the tuyre and forming inwardly directed converging air inlets therebetween, said tuyere being open atone end and being closed on the other end, a fuel feeding inlet orifice extending through the closed end of the tuyere, means for supplying fuel through said fuel feeding inlet orifice into the closed end of said tuyre adjacent the inner edges of at least some of the said air inlets, an enclosure surrounding said tuyere and fixedly secured to the open end, air supply means in communication with said enclosure whereby air under pressure will pass through said inwardly directed air inlets to form an outwardly moving vortical column of air within the tuyre and adjacent the wall thereof,

said column entraining fuel discharged into the tuyre to form a combustible air-fuel mixture, said. column inducing an inwardly directed flow of gas from the combustion chamber into the central part of the column, and an elongated combustion chamber comprising a chamber of revolution having a minimum diameter at least as great as the tuyere outlet and a maximum diameter approximately equal to its length and not more than three times the diameter of the tuyre outlet whereby vertical mixing in the tuyre is continued as vortical burning in the combustion chamber, said combustion chamber registering with the outlet of said tuyere.

4. A fluid fuel burner as claimed in claim 3 in ,seat therein, an axially and rotatably adjustable valve member cooperating with said seat to form an adjustable annular fuel injection orifice adjacent the inner ends of said air inlets, means for continuously supplying fuel through said orifice, means for manually rotating said valvewithout changing the axial adjustment thereof to clear said orifice of obstructions and means for supp y ng air under pressure through said air inlets between said blades for forming a hollow swirling axially outwardly moving fuel-air column in said tuyre.

WARD J. BLOOMER.

'BEFERENCES CITED The following references are of record in the file of this patent:

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